This experimental study focuses on the solidification of a ammonium chloride-water (NH4Cl-H2O) solution in a trapezoidal cavity with one and two vertical cooling walls. The effect of the initial concentration of ammonium chloride (sub-eutectic: f < 19.8% and eutectic f = 19.8%, where f is the percentage in weight) and boundary temperatures (Tcold = −30°C to −10°C) on the solidification process is examined. Particle Image Velocimetry (PIV) is used in this study to measure the velocity fields in the melt during the solidification process. The temperatures distributions at discrete locations in the solution and the boundary walls were measured by 32 thermocouples. The convection flow patterns; the ice shape and thickness; the velocity of the moving liquid/solid interface; and the temperature distribution were obtained. The convection patterns obtained for different initial concentrations showed significant differences. The results showed that the process of solidification is slower with an increase in the initial concentration levels of the binary solution. The growth rate of the frozen layer, the velocity of the moving solid-liquid interface and the temperature in the melt was significantly reduced when increasing the initial concentration of ammonium chloride.

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